The present invention relates to a device for wrapping groups of cigarettes.
In particular, the present invention relates to a wrapping device which may be used to advantage on cigarette packing machines, to which the following description refers purely by way of example.
Known packing machines normally comprise an input feedbox, from the outlet of which are withdrawn either layers of cigarettes subsequently combined into multilayer groups, or ready formed groups of cigarettes constituting the content of a packet. In general, such packing machines also comprise a first wrapping device whereby each group of cigarettes is inserted inside a folding spindle, on contacting the outer surface of which, a first sheet of wrapping material, normally consisting of foil, is folded to form the inner wrapping of the packet.
On known packing machines, each folding spindle normally comprises a tubular shell substantially in the form of a rectangular parallelepipedon, and in turn comprising flat lateral walls which, though thin, must be thick enough for the shell to withstand fairly severe stress. In view of the operating speed of modern packing machines, in fact, each folding spindle may be used for producing several inner wrappings a second, for each of which it is normally subjected to relatively severe tensile stress. On the other hand, since the inner wrapping is formed about the spindle, the respective group must be compressed inside the spindle before the sheet of wrapping material is folded, to enable the group, when extracted from the spindle, to expand elastically and so take up the slack corresponding to the thickness of the spindle walls, so that, the thicker the spindle walls are, the more each group must be compressed inside the spindle, thus increasing the risk of damaging the cigarettes in the group when forming the inner wrapping.